mmc: sdio: Check for CISTPL_VERS_1 buffer size

Before parsing CISTPL_VERS_1 structure check that its size is at least two
bytes to prevent buffer overflow.
Signed-off-by: Pali Rohár <pali@kernel.org>
Link: https://lore.kernel.org/r/20200727133837.19086-2-pali@kernel.orgSigned-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/sdio_cis.c

@@ -26,6 +26,9 @@ static int cistpl_vers_1(struct mmc_card *card, struct sdio_func *func,
 	unsigned i, nr_strings;
 	char **buffer, *string;
 
+	if (size < 2)
+		return 0;
+
 	/* Find all null-terminated (including zero length) strings in
 	   the TPLLV1_INFO field. Trailing garbage is ignored. */
 	buf += 2;